During the lifetime of a patient, it may be necessary to perform a total shoulder replacement procedure on the patient as a result of, for example, disease or trauma. In a total shoulder replacement procedure, a humeral component having a head portion is utilized to replace the natural head portion of the arm bone or humerus. The humeral component typically has an elongated intramedullary stem which is utilized to secure the humeral component to the patient's humerus. In such a total shoulder replacement procedure, the natural glenoid surface of the scapula is resurfaced or otherwise replaced with a glenoid component that provides a bearing surface for the head portion of the humeral component.
As alluded to above, the need for a shoulder replacement procedure may be created by the presence of any one of a number of conditions. One such condition is the deterioration of the patient's scapula in the area proximate to the glenoid surface as a result of, for example, glenohumeral arthritis. In such a condition, the erosion of the patient's scapula is generally observed posteriorly on the glenoid surface. Such erosion of the scapula renders treatment difficult, if not impossible, with a conventional glenoid prosthesis.
Referring now to FIG. 4 a prior art glenoid implant 1 is shown. Implant 1 includes a metal body to which a polyethylene glenoid bearing 3 is attached. A plurality of screws are used to secure the metal body to the glenoid. A central peg 5 may also be used to assist in securing the implant 1 to the glenoid.
Referring now to FIG. 3 a prior art glenoid bearing is shown as plastic glenoid bearing 6. The plastic glenoid bearing 6 includes a body 7 from which a plurality of pegs 8 extend. The plastic glenoid bearing 6 may also include a central peg 9, which likewise extends from the body 7 of the plastic glenoid bearing 6.
Referring now to FIG. 4, a prior art glenoid bearing is shown as metal backed glenoid bearing 1. The metal backed glenoid 1 includes a metal backing 2 and a plastic bearing 3. Screws 4 are used to secure the metal backing 2. A central post 5 may also be used to secure the metal backing 2.
Total shoulder replacement surgery includes the replacement of the humeral component and the glenoid component. The glenoid component is often the cause for a need of a revision. The need of a revision for a glenoid component is often due to the loosening of the glenoid component. Although there are many potential causes for loosening, there are no adequate solutions to the problem.
Polyethylene glenoids may wear and the polyethylene wear may lead to osteolysis and to aseptic wear loosening. Glenoid components have been provided which include a metal backing for fixation to the scapula and traditional snapped-in polyethylene components secured to the metal backed glenoid. These metal backed glenoids get better fixation, but tend to fail by polyethylene component disassociation from the metal backing. For a glenoid to be successful, the implant must be well fixed and the polyethylene must not disassociate itself from other components such as its metal backing.
The present invention is adapted to overcome at least some of the afore mentioned problems.